In recent years, with an increase in traffic volume on the Internet and the like, a larger transmission capacity is required. With the conventional transmission system via a copper cable, it is becoming difficult to achieve such a large transmission capacity. Optical communication has been therefore devised capable of achieving a larger transmission capacity.
Currently, in commonly used optical cables, a so-called physical contact (PC) method is adopted in which optical fibers face each other in a connector. However, in the PC method, highly accurate adjustment is required for alignment of both optical fibers. Furthermore, in the facing of the optical fibers, it is necessary to clean both the optical fibers each time the connection is made not to cause the optical fiber to be damaged due to adhesion of dust or the like to the tip of the optical fiber. Moreover, in the PC method, it is indispensable to inject a refractive index adjusting agent into the gap to suppress poor coupling in the gap at the tip of the optical fiber. As a result, it is difficult for general users to insert and remove optical fibers by the PC method.
As a method for solving these problems, a collimating optical coupling system has been devised. In the collimating optical coupling system, lenses are respectively mounted on the tips of the optical fibers with optical axes aligned with those of the optical fibers, and optical signals are made to be parallel lights and transmission of the optical signal is performed between the lenses facing each other. By using such a collimating optical coupling system, alignment accuracy is relaxed between the connectors of the optical fiber. Moreover, in the collimating optical coupling system, since the optical fibers are optically coupled with each other in a non-contact state, adverse effect is also suppressed on transmission quality due to dust or the like entering between the optical fibers, and frequent and careful cleaning is also unnecessary.
By the way, in principle, the parallel light used in the collimating optical coupling system is hard to attenuate even when it is away from the emitting portion, and depending on its intensity, it is difficult to satisfy the standards related to laser light, such as IEC 60825-1 and IEC 60825-2. Currently, a shutter is therefore provided in the optical connector for shielding the parallel light at the time of non-connection.
Furthermore, in Patent Document 1, an optical connector has been devised aiming for preventing a laser hazard due to collimated light (parallel light). Specifically, in an optical connector for performing collimating optical coupling, an optical connector is disclosed in which two uneven structures facing each other are provided in an optical fiber fixing portion and a collimating lens. In the optical connector, at the time of non-connection of the optical connector, the collimating lens is separated from the optical fiber fixing portion, and the uneven structure scatters light from the optical fiber. On the other hand, in the optical connector, at the time of connection of the optical connector, the collimating lens is pressed, whereby the collimating lens is in contact with the optical fiber fixing portion via the two uneven structures and emits parallel light.